TOKYO — The U.S. military will probably scale back plans to build key bases in Japan and Guam because of political obstacles and budget pressures, according to U.S. and Japanese officials, complicating the Obama administration’s efforts to strengthen its troop presence in Asia.

Under a deal announced Wednesday with Japanese officials, the U.S. government said it will accelerate plans to withdraw 8,000 Marines from the island of Okinawa. The decision came after several years of stalled talks to find a site for a new Marine base nearby.

Washington’s inability to resolve its basing arrangements on Okinawa, as well as the rising price tag of a related plan for a $23 billion military buildup on Guam, underscore the challenges facing the Obama administration as it seeks to make a strategic “pivot” toward the Pacific after a decade of fighting wars in Iraq and Afghanistan.

The Japanese government said it is still committed to a 2006 accord with the United States to find a new base location for other Marines who will remain on Okinawa. But officials in Tokyo acknowledged that they had made little progress in the face of fierce resistance from islanders opposed to the long-standing U.S. military presence there. Bleak public finances in the United States and in Japan have also undermined the effort.